Assessment of ultrasonography and computed tomography in the diagnostic strategy of suspected appendicitis
Poortman, P.
Citation
Poortman, P. (2009, October 29). Assessment of ultrasonography and computed tomography in the diagnostic strategy of suspected appendicitis.
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6
“All women of child-bearing age suspected of having acute appendicitis should undergo diagnostic laparoscopy prior to the planned appendicectomy, regardless of the certainty of the preoperative diagnosis”
PAUL BORGSTEIJN IN ‘ACUTE APPENDICITIS - A CLEAR CUT CASE IN MEN, A GUESSING GAME IN YOUNG WOMEN’, SURGICAL ENDOSCOPY 1997; 11:923-927
Ultrasonography and Clinical Observation in Women with Suspected Acute Appendicitis.
A Prospective Cohort Study
P. Poortman H.J.M. Oostvogel P.N.M. Lohle M.A. Cuesta
E.S.M. de Lange-de Klerk J.F Hamming
Digestive Surgery 2009; 26:163-168
Abstract
BACKGROUNDS/AIMS It was the aim of this study to evaluate the role of US and clinical observation in non-pregnant women of reproductive age with suspected appendicitis.
METHODS In a prospective cohort study, US was performed in 234 women with suspected appendicitis. Based on US findings and clinical assessment, 3 patient categories were established. Group A: unequivocal signs - laparoscopy (regardless US results); group B: equivocal signs - positive US - laparoscopy; group C: equivocal signs - negative US - observation. US results were compared with surgery, observation, and follow-up as the reference standard.
RESULTS The percentages of macroscopically infected appendices at laparoscopy in groups A, B and C were 76%, 55% and 5%, respectively. Group A: US was false negative in 27 of 128 (21%) women and false positive in 12 of 40 (30%) women. Group B plus C: US was false negative in 3 of 9 (33%) women and false positive in 5 of 57 (9%) women. Forty-six of 55 (84%) patients completed observation.
CONCLUSION Because of a high false negative rate, US as a sole imaging tool is of limited value both in women with unequivocal and in women with equivocal signs of appendicitis.
Observation is safe in women with equivocal signs of appendicitis.
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Ultrasonography and Clinical Observation in Women with Suspected Acute Appendicitis
Introduction
The clinical diagnosis of acute appendicitis as based on symptoms, physical findings and laboratory tests, is relatively inaccurate in females of reproductive age.1,2 If diagnostic laparoscopy is performed, the percentage of a normal appearing appendix can be as high as 20-50%; and in 10-25% an alternative diagnosis - mostly gynaecologic- is made as a possible explanation for the pain.1,2
Ultrasonography (US) and CT scanning have been described as methods for improving on the pre-operative diagnosis, CT having a better performance than US.3,4 However, in view of the radiation exposure, US is recommended for diagnosing young, female and slender patients.3,4
Especially in patients with atypical signs and symptoms, acute appendicitis can be managed by clinical observation besides additional imaging and diagnostic laparoscopy.5,6
In a prospective cohort study, the roles of US, diagnostic laparoscopy and clinical observation in fertile women with acute pain in the right lower abdomen suspected of acute appendicitis were evaluated.
Patients and Methods
All female patients between the ages of 13 and 45 years with acute right lower abdominal pain, suspected of acute appendicitis, and presented to the emergency department of a teaching hospital, were evaluated for inclusion in the present study. This study had been approved by the hospital’s ethical committee for human studies and all patients gave informed consent.
Exclusion criteria were known inflammatory bowel disease and pregnancy.
Clinical examination and baseline investigations (full blood count, urinanalysis and pregnancy test) were carried out. Included patients were evaluated by a senior surgical resident or a staff surgeon. The combination of rebound tenderness, fever (>37.50C) and leucocytosis (total white blood cell count >11.5 109 U/L) was regarded as a strong discriminator for acute appendicitis.7 Women positive for 2 or 3 of these signs were regarded as patients with unequivocal signs of appendicitis, needing acute surgery. Women positive for one of these signs were regarded as patients with equivocal signs. All patients underwent abdominal CT after clinical assessment. The US examinations were performed by resident radiologists and supervised by radiology staff members, who were alerted to “possible appendicitis”. The examination technique employed was that described by Puylaert.8 US assessments were based on criteria as derived from reports in literature.9 Direct visualization of an uncompressible appendix with an outer diameter of 6 mm or larger and echogenic
Table 1: Patient characteristics at presentation of 234 women suspected of appendicitis
Group A Group B Group C
Number of Patients 168 11 55
Age (yr) 26,1 (13-42 yrs) 25,9 (14-44 yrs) 26,8 (13-45 yrs)
Rebound tenderness 143 (85%) 4 (36%) 23 (42%)
Fever (>37.50C) 111 (66%) 3 (27%) 18 (33%)
Leucocytosis* 126 (75%) 4 (36%) 14 (25%)
*Leucocytosis=Elevated White Blood Cell Count (> 11.5 109 U/L)
incompressible periappendicular inflamed tissue were the primary criteria to establish the diagnosis of acute appendicitis. A fluid filled appendix, pericecal fluid and abscess were considered as secondary signs of acute appendicitis. In those cases where the appendix could not be indentified, yet abnormal amount of free fluid was seen, having thickened, dilated, or non-peristaltic bowel in the region of the cecum (suggesting perforation), these were reported as a positive result. The indication of a compressible right lower quadrant without an enlarged appendix or absence of secondary signs, were held as diagnostic criteria for a negative US result.
The reference standard was surgery, clinical observation and follow-up. Variables collected for each group included age, rebound tenderness, body temperature, total white blood cell count, rate of perforation, length of hospital stay and distribution of diagnoses.
Diagnostic laparoscopy was performed within 6-12 hours of patient arrival at the emergency department. The diagnosis of acute appendicitis at laparoscopy was made macroscopically.
All excised appendixes were microscopically analyzed. The histological diagnosis of appendicitis was based on infiltration of the muscularis propria by neutrophil granulocytes. A normal looking appendix was left intact.
Observation was performed by repeated clinical examination at 6-12 hourly intervals or more frequently, if considered necessary. In case of clinical deterioration, repeated laboratory tests were obtained. Patients, who developed signs and symptoms of acute appendicitis within 24 hours, underwent diagnostic laparoscopy. If signs and symptoms diminished, clinical
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Ultrasonography and Clinical Observation in Women with Suspected Acute Appendicitis
Table 2: Correlation of US and surgery/follow up findings for diagnosis of acute appendicitis in 234 patients
US in all 234 women
Positive Negative Total
Surgery/Follow Up
Positive 107 30 137
Negative 17 80 97
Total 124 110 234
US in 168 women with unequivocal signs and symptoms (group A)
Positive Negative Total
Surgery/Follow Up
Positive 101 27 128
Negative 12 28 40
Total 113 55 168
US in 66 women with equivocal signs and symptoms (group B+C)
Positive Negative Total
Surgery/Follow Up
Positive 6 3 9
Negative 5 52 57
Total 11 55 66
observation was terminated within 24-72 hours and patients were discharged. If signs and symptoms persisted after 48 hours of clinical observation, the surgeon could decide to perform a diagnostic laparoscopy or to continue clinical observation, depending on the severity of the clinical signs and symptoms.
Because the role of clinical observation was evaluated in the management of appendicitis, complications were divided into two categories: complications due to surgery, and complications due to clinical management. For each group, the results of US were recorded.
Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) version 14.0.
Results
Between January 2003 and December 2005, a total of 234 women were included in the study. Based on clinical signs and symptoms as well as US results, three patient categories
Table 3: Diagnostic laparoscopy in 234 fertile women with acute lower abdominal pain suspected for acute appendicitis
Group A Group B Group C
Diagnosis n (%) n (%) n (%)
Acute Appendicitis 128 (76%) 6 (55%) 3 (33%)
Number of Perforations 19 (11%) 0 (0%) 0 (0%)
Alternative diagnosis 20 (12%) 2 (18%) 3 (33%)
No diagnosis 20 (12%) 3 (27%) 3 (33%)
Total 168 (100%) 11 (100%) 9 (100%)
were assigned by the surgeon on duty:
Group A: unequivocal signs and symptoms of appendicitis-diagnostic laparoscopy (regardless of the US results-unless the latter contributed a diagnosis other than appendicitis and not amenable to surgery).
Group B: equivocal signs and symptoms of appendicitis and a positive US result-diagnostic laparoscopy.
Group C: equivocal signs and symptoms of appendicitis and a negative US result-clinical observation.
The characteristics of patients in the three different groups for age and clinical parameters (rebound tenderness, fever and leucocytosis) are reported in Table 1.
The US results are listed in Table 2. In 24 patients, US was assessed to be suboptimal because the appendix was not visible without secondary signs, or because the patient was obese or experiencing severe abdominal pain.
The results of findings at laparoscopy for each group are listed in Table 3. In Table 4 alternative findings made at surgery and US are listed. Five of the 25 (20%) alternative diagnoses defined at laparoscopy were detected by US.
In group C, during observation, the clinical situation of nine (16%) of the 55 women worsened within 48 hours and diagnostic laparoscopy was performed. Three patients appeared to have acute appendicitis (without perforation), in one patient a ruptured ovarian cyst was found, in one patient a torsion of the right ovary was found and in one patient Crohn’s disease was diagnosed. In three patients, no explanation for the pain could be established.
Clinical observation was completed in 46 of the 55 women. Although in these 46 patients
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Ultrasonography and Clinical Observation in Women with Suspected Acute Appendicitis
Table 4: Alternative diagnoses in 25 of 234 patients: laparoscopic and US findings N Laparoscopic diagnosis US diagnosis Action taken
5 Ovarian cyst 1 of 5 detected conservative
5 Corpus luteum haemorrhage not detected conservative 2 Adnexal teratoma 2 of 2 detected resection
2 Epidermoid cyst 2 of 2 detected resection
2 Cyst of Morgangi - torsion 1 of 2 detected resection 5 Endometriosis/PID 0 of 5 detected conservative 2 Suspected chlamydia infection 0 of 5 detected conservative 1 Femoral herniation 0 of 1 detected correction 1 Crohn’s disease (suspected) suspected no resection 25
no signs and symptoms of acute appendicitis occurred after 48 hours of observation , 10 of the 46 patients were not discharged. Reasons for prolonged clinical observation are listed in Table 5.
Most of these 10 patients needed prolonged clinical observation due to diagnostic reasons such as additional CT scanning or consultation of other specialists. In eight of these 10 patients, a diagnosis could be established during this period of clinical observation. In two of these 10 patients, no diagnosis could be established, despite longer clinical observation and additional CT scanning.
The overall length of hospital stay for all 234 patients ranged from 1 to 17 days with a median of 3 days. For group A, the length of stay was 1 to 17 days with a median of 3 days, for group B, the length of stay was 1 to 5 days with a median of 2 days. For group C, the length of stay was 1 to 8 days with a median of 4 days. The mean follow up period was 18 months, ranging from 3 months to 2 years.
Complications occurred in 13 of the 234 patients (6%). Complications due to surgery in group A occurred in 8 patients: three patients with perforated appendicitis needed a transrectal drainage of a pelvic abscess, one patient developed a wound abscess, one other patient with perforated appendicitis needed admittance to the ICU because of respiratory failure, one patient developed aspiration pneumonia and two other patients were re-admitted after laparoscopic appendectomy and observed in the hospital because of recurrent lower abdominal pain. One complication due to clinical management occurred in group A: one
Table 5: 10 patients with persistent clinical observation: diagnosis, modality allowing the final diagnosis and length of hospital stay
Diagnosis Modality Length of hospital stay (days)
1. Adhesions (previous abdominal operations) Clinical diagnosis 4
2. Duodenal ulcer Gastroduodenoscopy 4
3. Diverticulitis CT scan 4
4. Adhesions (previous abdominal operations) Clinical diagnosis 3
5. Endometriosis Gynaecologist 3
6. Urinary tract infection Urologist 4
7. Pneumonia X-ray – CT scan 7
8. Gastro-enteritis Internal medicine 5
9. Diagnostic considerations - no diagnosis CT scan 7 10. Diagnostic considerations - no diagnosis CT scan 8
patient in which the supposed unaffected appendix was left in place was readmitted; at the secondary laparoscopy, acute appendicitis was diagnosed and appendectomy was performed. In group B, one complication due to surgery occurred: one patient developed a wound abscess. In this group no complications due to clinical management took place.
In group C, no complication related to surgery occurred, in 3 patients complications due to clinical management did occur: because of persistent right lower abdominal pain they were re-admitted, two of these women underwent diagnostic laparoscopy and appeared to have acute appendicitis. In one woman, the diagnosis turned out to be endometriosis.
Microscopic evidence of acute appendicitis was seen at histology in 135 excised appendices,.
In two patients, the appendix was microscopically normal although the surgeon diagnosed an acute appendicitis. Because of conversion to a split muscle incision, nine macroscopically normal appendices were removed. This was confirmed at histology.
Statistical Data
Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of US for group A and group B plus group C, including 95% CI, are shown in Table 6.
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Ultrasonography and Clinical Observation in Women with Suspected Acute Appendicitis Table 6. Statistical data of US in group A and group B plus C
Sensitivity Specificity PPV* NPV* Accuracy
Group A (95% CI)
79%
(71%-85%)
70%
(55%-82%)
89%
(82%-94%)
51%
(38%-64%)
77%
(70%-83%) Group B+C
(95% CI)
67%
(35%-88%)
91%
(81%-96%)
55%
(28%-79%)
95%
(85%-98%)
88%
(78%-94%)
Difference 12% -21% 34% -44% -11%
*PPV = Positive Predictive Value *NPV = Negative Predictive Value
Discussion
This prospective cohort study confirms other previous studies that in women of reproductive age with suspected appendicitis, the overall negative appendicitis rate may vary from 20 to 50%.1,2 To improve diagnostic accuracy, US and CT have been recommended.9 Although CT shows to have a better test performance, several authors make a case for US as the primary imaging modality for a select patient subgroup (young, female and slender patients ) where radiation exposure is especially relevant.3,4
In few prospective studies, the value of US in the management of acute appendicitis in specifically women of childbearing age has been reported,10,11,12 but as far as we know ours is the first prospective study evaluating the value of US and clinical observation in women with typical and atypical findings of acute appendicitis. Wilson et al. prospectively evaluated the influence of pre-operative US on the management of 49 women (and 50 men) suspected of appendicitis and for none of these women, US was helpful.10 Douglas et al.
prospectively determined that US improves clinical outcomes for patients (146 women and 156 men) suspected of appendicitis and although US yielded a diagnostic accuracy of 93% it has not been shown that the diagnosis of appendicitis aided by US produces better outcomes than clinical diagnosis alone.12 Garcia-Aguayo et al. conclude in a prospective study on patients suspected of appendicitis (213 women and 161 men) that US offers benefit for patients with a moderate clinical probability of appendicitis, but is of little utility in women with a high clinical probability of appendicitis.11 These results are confirmed in our study. In women highly suspected of appendicitis, the accuracy of US was 77%, comparable with the accuracy of the clinical diagnosis in this study (76%) and with historic values.1,2,9 In 27 (21%) of the 128 women with acute appendicitis, US was negative. This means that a negative US result cannot rule out appendicitis, which implies that in women with typical
signs of appendicitis, US seems to have limited value. The value of US in patients with equivocal signs has also been reported in other studies.13,14,15 In a meta-analysis on 3.358 patients with suspected appendicitis, Orr et al. conclude that US should not be used to exclude appendicitis in patients highly suspected of appendicitis; for these patients surgery is recommended. However, patients with atypical findings should have an operation if US is positive, otherwise the patient should be observed.13 Although this management is described in our study, the value of US for women with equivocal findings can be questioned.
While the amount of women with atypical clinical findings is much smaller than women with unequivocal signs (66 vs 168 women) US was negative in 3 of the 9 women having acute appendicitis. This suggests that US is of limited value for women with equivocal signs of appendicitis; nevertheless, a definitive conclusion needs to be cautiously drawn because the size of the group with atypical signs we studied was small. A negative US may support the surgeon in his conviction that clinical observation can be safe, yet according to our data, US actually adds little to the decision to observe the patient on clinical grounds. In the present study, 46 of 55 women (84%) with atypical clinical findings, clinical observation was completed without surgery.
This shows that in women with an equivocal presentation clinical observation can be used as a safe method. The worth of conservative management is also reported in other studies.5,6,16 The main inconvenience of expectant management approach may be the recurrence of mild appendicitis. Evidence suggests that spontaneous resolution of untreated, non-perforated appendicitis is common.17 Some patients might represent unrecognized cases of self- limiting appendicitis. In our study, this may have resulted in underestimation of false negative results. However, this is also applied to the results of other studies published on this topic.
During follow up, two women, who had been clinically observed initially, were re-admitted and laparoscopic appendectomy was performed because of acute appendicitis.
In our study, the reason for 17 false positive US findings was the fact that the appendix was larger than 6.0 mm (varying from 8-10 mm), which is the accepted, current limit of normal. During graded compression, the relevant anteroposterior diameter of the appendix may vary and combined with an experience of pain in the right lower abdominal region while undergoing the US performance, the radiologist had assessed US positive for appendicitis. The reason for 30 false negative US findings was the inability to visualize the appendix without secondary signs of acute appendicitis.
Acute appendicitis in women of childbearing age may be mimicked by a range of gynaecological pathologies. The present study shows that in this specific patient category, laparoscopy proves to be useful to identify acute gastro-intestinal and gynaecological disorders that can mimic acute appendicitis. Using US allowed detection of most of the
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Ultrasonography and Clinical Observation in Women with Suspected Acute Appendicitis
alternative surgical diagnoses. Yet, most of the self- limiting gynaecologic diagnoses were not detected by US. In acute gynecologic etiologies in early conditions endovaginal pelvic ultrasound is probably more valuable.18
Some authors suggest implementing US during management of all patients with suspected appendicitis.8,19,20,21 These studies, performed in an academic setting by experienced body imaging radiologists, report high diagnostic accuracies varying from 84% to 98%. In our clinical setting, US imaging was performed by residents supervised by body imaging radiologists and by general radiologists. This might have resulted in a lower accuracy of US.
However, our study set-up probably represents more closely the common clinical setting in an average hospital. As mentioned earlier, CT has been recommended to improve diagnostic accuracy in women of childbearing age.22,23 In our study, CT was not implemented as a diagnostic modality before laparoscopy was performed. We realize that CT could have provided more information yet the aim of our study was to assess the value of US with surgery as the reference standard. To implement US as well as CT in the diagnosis of acute appendicitis, a diagnostic pathway has been described in which an additional CT can be undertaken in case of a negative or inconclusive US.21,24 To lower the negative appendicitis rate in women with unequivocal signs of appendicitis, applying US as the single imaging modality is not sufficient because of a high rate of false negative or inconclusive US. As described above, we suggest a diagnostic pathway with the primary use of US and, in case of a negative or inconclusive US, an additional CT. False positive US findings will still result in a certain negative appendicitis rate, yet applying US as a primary imaging modality can prevent the disadvantages of CT, especially regarding patient preparation, contrast material administration, and radiation exposure. Further prospective studies with special interest in the value of this diagnostic pathway in women suspected of appendicitis are needed.
In conclusion, because of a high false negative rate, US as a sole imaging tool is of limited value both in women with unequivocal and in women with equivocal signs of acute appendicitis. Observation is safe in women with equivocal signs of appendicitis.
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